BIG SKY -- Cawing ravens gave Dave Christianson his first clue that something was afoot in the animal kingdom between Big Sky and West Yellowstone.

One day earlier, Christianson had spotted elk on a hill and wolves on a nearby ridge. Now he saw only ravens and wondered if their presence signaled another back country battle in the Taylor Fork Drainage.

"Most of the time, we find kills because of ravens or magpies," said Christianson, a Montana State University graduate student from Glasgow.

"We're going to see if we can go find it," said Scott Creel, an MSU ecologist and Christianson's advisor.

Christianson and Creel are researching elk in the northwest part of the Yellowstone Ecosystem to see how they're affected by wolves. From previous years, they know that wolves cause elk to change herd sizes, behavior patterns and use of the landscape. Now, the researchers are trying to understand how these changes affect the elks' nutrition, reproduction and survival.

From January into spring, Christianson lives during the week in a one-room bunkhouse off U.S. 191. He spends his days doing things like spotting elk and wolves, inspecting tracks and scrutinizing videotapes of the animals. Creel generally drives down from Bozeman every Wednesday to join Christianson on his rounds.

Every two weeks, the researchers follow elk paths through the Porcupine, Taylor and Tepee/Daly drainages, recording where the elk have traveled and fed and what plants they have eaten. Sometimes, they drop a lead ball or pound the snow with an imitation hoof to see how hard the elk had to work to get through the snow to a meal. It's all to see how wolves affect how well the elk are feeding and how hard the elk have to work for a meal.

This day was somewhat different, though. With an unsolved mystery pulling them toward Cameron Draw, Christianson slipped into cross-country skis while Creel donned snowshoes. Both wearing backpacks, they trudged and glided across a field and up a ravine. They stopped to take photos. They pushed branches aside. They finally came upon blood splatters in the snow, stiff brown hair in a hole, rumen near a log and tracks on a hill.

It was a battle scene without a body, a combat zone without troops.

"This is odd that there isn't much here," Creel said.

Christianson added, "Usually the entire skeleton is here."

Looking for more clues and additional remains, Christianson headed up the ridge where he had seen the wolves the day before. Creel clambered up the opposite side.

"One of them sat here and ate a big chunk of it," Creel yelled. "I'm going to climb higher."

Several minutes later, the researchers returned, Creel with an elk hide and Christianson with a pelvis, two femurs and part of a skull. It appeared, they said, that wolves had killed an eight-month old elk on the side of the hill. As the wolves fed on the calf, the carcass had slipped toward the ravine. The wolves retrieved it and hauled it up to the ridges, evidently still chewing on it the next day. When Creel reached the top of the hill, he found wolf tracks, drag marks and three freshly melted-out beds.

"I think they were up there eating away when we arrived or shortly before," Creel said.

Bone marrow revealed that the elk calf had been suffering even before the wolves attacked it, Christianson said as he cut through one of its bones. An elk with plenty of food has bone marrow that looks like thick Crisco, he said. This marrow was watery and deep red, indicating that the elk was slowly starving and starting to digest the fat in its marrow.

This was Christianson's fourth winter near Big Sky and his final season in the field. With results published recently in the journals Animal Behavior and Ecology, the researchers have found that the number of elk calves in their study area has declined, but not because they were eaten by wolves. Wolves, in fact, rarely kill elk in the first six months of the elks' lives.

"This year, bears were far and away the main predators in the first six months," Creel said. "That was a surprise to us, but it confirms what P.J. White and Doug Smith have also seen with wolves and elk in other parts of Yellowstone. If the calves are missing, but wolves are rarely killing them in the first six months, what's going on?"

It appears that one effect of changed behavior is lower pregnancy rates, Creel said. Preliminary data from the Gallatin Canyon, Yellowstone National Park, the Madison Valley, Paradise Valley and Elkhorn show that elk pregnancy rates have declined where wolves are most active. The elk -- especially females -- spend less time eating and more time watching for predators when wolves are around.

"They just say, ‛Today the job is to avoid being killed,'" Creel said. "So they're probably not as efficient at foraging. That's what Dave (Christianson) is studying now."

Unsuccessful this time at staying alive, the elk remains they discovered represented the ninth wolf kill they'd seen in a month, the researchers said as they returned through U.S. Forest Service land to their vehicles. This area of the Taylor Fork contains approximately 250 elk.